In the context of communication receivers, a potentially attractive solution for emerging low-cost and flexible radio architectures utilize zero-IF receivers that perform direct conversion to baseband through complex in-phase and quadrature (I/Q) down conversion mixers. A problem of such mixers is however that they, due to analog mismatch errors, exhibit an imbalance between the I and Q channels which causes a large mirror-frequency interference, corresponding to an unwanted contribution of the complex conjugate of the desired signal. The interference may e.g. be 50-100 dB stronger than the desired signal whereas the mixers alone may e.g. only provide some 30-40 dB attenuation, which obviously is insufficient in such cases. Therefore, there is a need to add additional digital circuitry in order to compensate for the I/Q channel mismatches (imbalances). In narrow-band applications it may suffice to model the interference as frequency independent, and the mismatch and compensation may then be done via two multiplier coefficients. With increasing bandwidths, it is however necessary to instead make use of frequency-dependent quantities for the I/Q channel mismatch modeling and compensation, including estimation of the mismatch. Such solutions for compensating the I/Q channel mismatch and that directly or indirectly comprise estimation of the I/Q channel mismatch are for example disclosed in:    L. Yu and W. Snelgrove, “A novel adaptive mismatch cancellation system for quadrature IF radio receivers,” IEEE Trans. Circuits Syst. II: Analog and Digital Signal Processing, vol. 46, no. 6, pp. 789-801, June 1999,    K. Pun, J. Franca, C. Azeredo-Leme, C. Chan, and C. Choy, “Correction of frequency-dependent I/Q mismatches in quadrature receivers,” Electronics Lett., vol. 37, no. 23, pp. 1415-1417, November 2001,    G. Xing, M. Shen, and H. Liu, “Frequency offset and I/Q imbalance compensation for direct-conversion receivers,” IEEE Trans. Wireless Comm., vol. 4, no. 2, pp. 673-680, March 2005,    B. Kirei, M. Neag, and M. Topa, “Blind frequency-selective I/Q mismatch compensation using subband processing,” IEEE Trans. Circuits Syst. II: Express Briefs, vol. 59, no. 5, pp. 302-306, May 2012, and    Anttila, M. Valkama, and M. Renfors, “Circularity-based I/Q imbalance compensation in wideband direct-conversion receivers,” IEEE Trans. Vehicular Technology, vol. 57, no. 4, pp. 2099-2113, July 2008.